This species was originally described as Simpsonichthys nielseni.

W. Costa (2006) assigned many members of the genus Simpsonichthys to the subgenus Hypsolebias (Costa 2006). Hypsolebias was subsequently elevated to a genus (Costa 2011). According to some scientists, the separation of Hypsolebias from the genus Simpsonichthys is insufficiently substantiated and, therefore, debatable.

Type locality: Hypsolebias nielseni was described by W. Costa in 2005 from a temporary pool in Pirapora, rio São Francisco floodplains, altitude 500 m, Estado de Minas Gerais, Brazil. Coord. 17º21’59.6”S 44º56’32.3”W

Discoverer(s): Dalton Nielsen, January 1987 (for the types : W.J.E.M. Costa and Claudia P. Bove, January 22. 2005).

Etymology: It was named after the Brazilian scientist Dalton Nielsen to honor his contribution to science as collecter and hobbyist.

Diagnosis: 

distinguished from all congeners in having 6 or 7 light greenish yellow flames on male caudal fin ; similar to H. stellatus and

distinguished from all other components of the H. notatus superspecies by possessing a row of elongated light spots alternating with black interspaces on the basal portion of the dorsal fin in male (vs. never a similar color pattern) ; differs from H. stellatus in having caudal fin greenish yellow in male (vs. dark brownish red) and by the absence of a dark gray to black distal stripe on the anal fin in male (vs. presence) (Costa, 2005).

This species can be productive, and the fry is small. Immediately after hatching, the fry should be fed with freshly hatched Artemia nauplii (brine shrimp) or better Paramecium. As most annual species do, they spawn by diving entirely into the substrate. It is best to provide a container with a lid on top in which a hole is made to allow the fish access. That container will need to have enough peat in it for the fish to dive completely into it. For most Hypsolebias species, egg development is complete after 8-10 weeks. However, it is wise also to check a few weeks earlier to see if any eggs have fully developed. Do not let the peat dry too far because the Hypsolebias like it moist. The development will be slower at storage temperatures between 21 and 24 Celsius and speed up at 25-29 Celsius. Before watering the eggs, put some eggs in the water of

about 18-20 degrees Celsius to see if the eggs hatch correctly. That usually happens within 2-6 hours. Then, if eggs hatched well and fry, swim correctly, bring all remaining peat in the water. You may need to re-pack the peat after pouring over the first group of fry to a larger tank. With regular water changes and sufficient food, the young will grow quickly, and after about 5-6 weeks, they can already produce their first eggs. Since this genus has an annual life cycle, the expected life span in captivity is not much more than 10 to 12 months. Their life expectancy is limited to when their pool still has water in the wild. This period can vary from 6 to 8 months.

Remark:

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Max. size 5.0 cm.
Dorsal 21.5,
Anal 20.0,
D/A -3.0,
LL scale count (average)26.5
Pre- dorsal length to % SL – 45.3 %
Depth to % SL – 36.4 %